1. Field of the Invention
The present invention relates to an oil pressure control system for an automatic transmission system for use with automobiles.
2. Description of the Prior Art.
In an automatic transmission system for use with automobiles which includes a fluid torque converter, a transmission gear and friction engaging means for establishing a selected transmission engagement in said transmission gear and is adapted to be controlled by an oil pressure control system, an accummulator is generally provided in an oil pressure circuit for operating said friction engaging means in order to accomplish a smooth transition of the automatic transmission system by reducing the shock which is caused by the engagement of the friction engaging means. An accumulator for the abovementioned purpose conventionally comprises a fluid displacing element such as a cylinder-piston means, wherein the piston is flexibly supported by a spring means which counteracts the oil pressure existing in the oil pressure circuit for operating the friction engaging means. However, it would be desirable if the buffering performance of the accumulator is adjusted according to the torque transmitted by the transmission system so that, for example, the stiffness in the buffering operation of the accumulator increases as the engine torque increases.